Dental casting machine



Sept. 19, 1933.

F. S. MEYER DENTAL CASTING MACHINE Filed March 1 6, 1931 2 Sheets-Sheet 1 Sept. 19, 1933 s MEYER 1,927,571

DENTAL CASTING MACHINE Filed March 16, 1931 2 Sheets-Sheet 2 Patented Sept. 19, 1933 UNITED STATES PATENT OFFICE Application March 16, 1931.

4 Claims.

pressure.

Such machines are extensively utilized at this time for preparing metal inlays, crownsand bridge. work for the most part requiring a separate and independently connected blow torch for melting the gold or other metal substance used for the casting and a source of gas under considerable pressure, such as compressed air for forcing the molten gold into the mold cavity. In a number of such devices a pressure reducing valve is utilized to obtain the correct pressure on the molten gold.

It is an object of my invention to provide a comparatively simple and highly eflicient pressure casting machine utilizing a single source of gas under pressure for both forcing the molten metal into the mold and for aiding the combustion of the fuel of the blow torch and having simple, accurate and highly efiicient means for regulating and determining the pressures utilized as well as for regulating the mixture of the hydro-carbon fuel and the combustion'supporting gas in the blow torch.

It is a further object to provide a casting machine of the class described which will successfully operate upon molds varying considerably in dimensions, provision being made to support and accommodate molds of different heights and diameters in such manner that upon the same movement or sliding of the gas discharge plunger, the crucible ends of molds varying in height will be sealed and simultaneously the gas control valve will be opened for forcing the molten metal into the mold.

Another object is to provide such a casting machine having a blow torch or analogous heating means supplied with combustion supporting gas from the gaseous medium for forcing the molten metal into the mold and supplied with a combustive gas from an independent source such as a gas outlet which is usually available in a dentists office or laboratory. This combination greatly expedites the melting of the gold in that the flame applied is much hotter than with the ordinary pressure casting machine since oxygen or nitrous oxide is preferably utilized and further since the blow torch utilized may be manipulated or directed manually upon the gold from various angles. A further important factor is that by the use of a combustion supporting gas for forcing the gold into the mold the gold is kept in a viscous Serial No. 522,904

state and will thoroughly fill all interstices of the mold cavity.

. Another object is to provide in a pressure casting machine an improved gas control valve actuated and opened by the movement of a piston, the lower end of which carries a seal for engagement with a mold orinvestment ring and having associated therewith means for automatically locking the piston in mold-sealing position after the mold has been sealed and the gas-escape valve opened.

Theseand other objects and advantages of the invention wfll be more fully set forth in the following description made in connection with the accompanying drawings, in which like reference characters refer to similar parts throughout the several views, and in which:-

Fig. 1 is a front elevation of an embodiment of my invention;

Fig. 2 is a view of the machine taken mostly in side elevation the gas discharging plunger and associated parts, however, being shown in vertical section;

Fig. 3 is an enlarged vertical section showing the details of the gas discharge valve and sealing head of the gas discharge plunger;

Fig. 4 is a detail plan view showing the plate or bed upon which the investment rings and molds are supported;

Fig. 5 is a bottom plan view of the sealing head carried by the lower end of the gas discharge plunger;

Figs. 6 and 7 are top plan views of removable supporting members adapted to be associated with the bed for use with certain size investment rings, and

Figs. 8 and 9 are cross sections taken on the lines 8-8 and 9-9 of Figs. 6 and '7 respectively.

In the form of my invention illustrated the several pieces of apparatus are supported from a heavy pedestal which may if desired be in the form of a metal casting having a broad base 10 and an upstanding sleeve or socket 10a adapted to receive tank T containing a combustion supporting gas such as oxygen or nitrous oxide under considerable pressure. Pedestal 10 carries, also, a laterally projecting bracket 10b terminating in a vertically disposed open ended cylinder 100 within which the upper end of a gas discharging plunger 12 is slidably mounted. Socket 10a of. the pedestal may be provided with a series of set screws 11 adapted to be adjusted to clamp and secure tanks T which may vary considerably in diameter.

The gas discharging plunger 12 has an axial 2 passage therethrough connected at its upper end with a vertical tube 13 provided with a nipple 1301. which may be connected by a flexible conduit 14 with the source of gas supply for forcing the molten metal into the mold. The upper end of cylinder 100 may be provided with a suitable threaded cap 15 which is apertured to accommodate vertical conduit 13.-

A vertically disposed rack 12a is provided on the inner portion of plunger 12 and is engaged by a gear segment 16 which is fixed to a rock shaft 17 suitably journaled in bracket 10b. Rock shaft 17 is provided with an operating lever or handle 18 disposed at one of the sides of the supporting pedestal by which the plunger may be raised or lowered in cylinder 100. A horizontal spring pressed bolt 19 is mounted in a boss adjacent the upper end of cylinder 10c and adapted to engage a recess 12b in the outer longitudinal edge of plunger 12 to hold the plunger in raised position. When the plunger is depressed or lowered to the position indicated in dotted lines in Fig. 2, bolt 19 will abut the upper end of plunger 1 12 looking the plunger in the depressed position.

The withdrawal of bolt 19 may be effected by means of an externally disposed knob 19a.

A combination gas discharge and mold sealing head, indicated as an entirety by the letter H is mounted on the lower end of gas discharge plunger 12. As clearly shown in Fig. 3, head H comprises a sleeve 20 having an inturned flange at its upper end adapted to abut a ring or annular shoulder 21 which surrounds a nipple 22 tapped into the lower end of plunger 12. The inturned flange of sleeve 20 surrounds the exterior of the lower end of plunger 12 and is mounted thereon for limited upward sliding movement. Nipple 22 is provided with an axial valve chamber 22a in the upper portion thereof having a valve seat in communication with a reduced axial passage 22b in the lower portion of the nipple. As shown a ball valve 23 is disposed in valve chamber 22a urged against its seat by means of a coiled spring 24 which is interposed between said ball and an abutment ring 25 fitted below a diametric stop pin 25a passed through the upper end of nipple 22. A pump washer 26 is clamped between ring 21 and the head of nipple 22 and the nipple is provided with a lateral gas discharge port 220 disposed below said washer. A valve release pin 27 projects axially from the depending end of nipple 22, the upper end of said pin being normally disposed slightly below ball valve 23 and the lower end of said pin being normally in abutment with the central imperforate portion of a sealing disk 28. A coil spring S is interposed between the shoulder of nipple 22 and sealing disk 28.

Sealing disk 28 is of adequate diameter to cover the crucible end of the largest size mold or investment ring utilized in dental work and is provided on its lower face with a series of concentrically disposed sealing rings 29 which may be constructed of suitable compressible material, said rings being of proper diameter to engage and seal the edges of various sized investment rings. The disk 28 is also provided with a series, as shown 4, of circumferentially arranged discharge ports 28a. through which the oxygen or other gas under pressureis distributed upon the molten metal in the crucible of the mold.

The upper end of tank T is provided with the usual neck 30 having mounted therein a diametrically extending discharge valve. A suitable pressure reducing valve, indicated as an entirety by the letter V is clamped to gas tank neck 30 in the conventional manner the bracket 31 of said pressure reducing valve including the usual gas intake 32 which is engaged with the lateral gas discharge of the tank connection 30, the discharge valve of the tank being opened by means of a screw plunger 33 which also serves to clamp the pressure valve to the connection 30. Pressure valve V is regulated by a suitable handle 34 and two indicators or dials A and B are connected with the pressure reducer valve, indicator A showing the pressure of the gas in tank T while indicator B shows the reduced pressure at the outlet side of the valve V. Valve V is provided with a discharge nipple 35 which is connected by flexible conduit 14 with the gas discharge plunger 12.. Pressure reducer valve V. has a second discharge passage 36 which may be tapped into a valve'chamber 37 which has disposed therein a regulating valve 38 preferably of the needle type. Valve chamber 37 may be formed a second valve chamber 39 through which the combustive gas may pass. Valve chamber 39 is provided with a regulating valve 40 for controlling the amount of combustive gas admitted to a mix ing chamber 41 which communicates with the two valve chambers 3'7 and 39. The combustive gas may be furnished to valve chamber 39 through a conduit 42 which may be connected with a commercial source of illuminating gas, such as an outlet provided in the dentists ofilce. Mixing chamber 41 is provided with a nipple 41a which may be connected by a flexible conduit 43 with a small blow torch 44. Blow torch 44, as shown, comprises a tube having a laterally extended outer end provided with an adjustable discharge nozzle. A retaining element or hook 45 is mounted on the front face of pressure reducing valve V to support the torch and conduit when the same are not in use.

Base 10 of my supporting pedestal is provided with'a projecting support 10d disposed in spaced relation below the sealing disk 28 and said support is perforated to permit passage of the operating gaseous medium therethrough. p

In the preparation of dental castings, mold casings or investment rings varying considerably in height and diameter are utilized. Since longitudinal movement of gas discharge plunger 12 .is definite, I find it necessary to provide means integrally with for supporting molds and investment rings of different heights in such manner that in each instance the crucible end of the mold will be sealed by disk 28 when the gas discharge plunger is slidably moved to its lowermost position. While I contemplate other means for the above described purpose, the simplified series of supports illustrated in Figs. 6 to 9 inclusive and Fig. 2 have been found entirely satisfactory. A circular bed 46 is fixed to the top of support 1011 axially aligned with the sealing disk 28 and this bed preferably has an upstanding annular flange 46a which is adapted to hold a removable mold supporting disk 47. Bed 46 has a concentric shoulder 46b which is adapted to receive and nest another support ing disk 48, see Figs. '7 and 9, of considerably greater thickness than disk 4'7. Bed 46 has a central aperture adapted to receive a third disk or supporting cylinder 49, see Fig. 2, of smaller diameter than disk 48.

The largest size mold and investment ring is accommodated in the bed 46; the next smaller size is accommodated in disk 47; the next smaller size is accommodated in disk 48 and the smallest size mold is accommodated in the supporting cylinder 49. Each of the mold supports and also the bed is provided with central apertures and centrally disposed recessed portions to permit the unrestricted discharge of the gaseous medium which forces the gold into the mold cavity and which passes through the porous mold in the operation of the casting machine.

Operation In operation the gas discharge plunger is positioned as shown in Fig. 1, the combined gas discharge and mold seating head being held in extreme downward position by means of the large coil spring S which is interposed between the sealing disk 28 and the shoulder of nipple 22. Pressure valve V is adjusted by handle 34 to insure proper pressure of the gas through discharge passages 35 and 36. This may be easily ascertained by observing the gauge B. The mold casing or investment ring I with the mold M therein is then supported upon the appropriate support below the sealing head with the crucible end of the mold upward. Small pieces of the gold or other metal to be used for the casting are placed in the crucible of the mold and the regulating valves 38 and 40 are properly adjusted to produce a hot flame when the blow torch is ignited. The blow torch is manipulated by the operator directing the flame on the gold in the crucible of the mold from different angles to quickly melt and liquefy the gold. With my device a very hot flame is produced, since anef ficient combustion supporting gas such as oxygen or nitrous oxide is mixed with the combustive gas. When the gold is properly melted, handle or lever 18 is swung downwardly causing the gas discharging plunger, and with it the combination gas discharge and mold sealing head, to be moved downwardly to extreme position. The sealing disk 28 engages the upper edge of the investment ring before extreme position is reached causing the gas discharge and mold sealing head to slide upwardly relative to the lower end of gas discharge plunger 12 against the tension of coil spring S. This relative sliding of the head 20 causes valve release pin 27 to lift the ball valve 23 from its seat releasing the operating gas which forces the molten metal into the mold cavity and passes through the porous mold and is exhausted through the apertures in the mold support and supporting portion 10d of the base. A perfect seal is efiected between the sealing ring 28 and the upper edge of the investment ring prior to the release of the gaseous medium and the gas discharge plunger is locked in lowered position by means of the engagement of bolt 19 with the upper end thereof. The release of the combustion supporting gas used as the operating medium efiects the furthenheating of the gold andinsures a perfect sealing of all crevices of the mold cavity. The gas discharge plunger and the head H may be retracted by releasing spring pressed bolt 19.

From the foregoing description it will be seen that I have provided a highly efiicient and scientific casting machine utilizing a single source of gas under pressure for both forcing the molten metal into the mold and for aiding the combustion of the fuel of the blow torch and having accurate means for regulating and determining the pressures utilized as well as for controlling the mixture of the gases supplied to the blow torch 'or other heating medium.

Extensive usage has shown the device to be highly efficient for all purposes intended and substantially perfect castings have been obtained continuously with the use thereof.

It will, of course, be understood that various changes may be made in the form, details, proportions and arrangement of the parts, without departing from the scope of my invention, which, generally stated, consists in a device capable of carrying out the objects above set forth, and in the novel parts and combinations of parts disclosed and defined in the appended claims.

What is claimed is:-

1. In a dental casting machine, a relatively heavy support, a tank containing a combustion supporting gas under pressure, a pressure reducing valve connected with said tank and having two outlet passages, a gas discharge plunger slidably mounted in said support for vertical movement and having a combination gas discharge and sealing head carried at the lower end thereof, means for supporting a mold below said sealing head, a connection between one of said outlet passages and said gas discharge plunger, a

blow torch flexibly connected with said second outlet passage for independent manual manipulation, a valve in said gas discharge plunger and means for suddenly opening said valve and valve means for controlling the flow of gas through said blow torch.

2. A dental casting machine having in combination a support, a tank containing combustion supporting gas under pressure and mounted in said support, a pressure reducing valve secured to and supported by the upper end of said tank and having two discharge passages, a gas dischargeplunger slidably mounted in said support for vertical movement, a combination gas discharge and sealing head carried at the outer end of said gas discharge plunger, a valve in said plunger normally held in closed position, a connection between said plunger and one of the discharge passages of said pressure reducing valve, a mixing chamber connected with the second of said discharge passages and also with a source of combustive gas, a blow torch flexibly connected with said mixing chamber adapted to be manually directed as desired and manipulated to melt the metal in the crucible po tion of a mold and means for actuating said gas discharge plunger to substantially simultaneously effect a sealed joint between said sealing head and one end of the mold and to open said valve plunger.

3. In a dental casting machine, a supporting base having a large vertical socket, a tank containing combustion supporting gas detachably secured in said socket, a pressure reducing valve detachably secured to and supported from the upper end of said tank and having communication therewith said pressure reducing valve having two outlet passages, a mixing chamber supported from said pressure reducing valve and having communication with one of said outlet passages, said mixing chamber also aving communication with a source of combustive gas, a discharge for said mixing chamber, a manually manipulatable blow and said gas discharge torch connected by a flexible conduit with the discharge of said mixing chamber, said support having an overhanging arm, a vertically reciprocable gas discharge plunger slidably mounted in said overhanging arm and having a gas dis--' charge and sealing head at the lower end thereof, a connection between the upper end of said gas discharge plunger and the second outlet of said pressure reducing valve, a valve in said gas dis- 4- charge plunger and means for suddenly opening said valve.

4. In a dental casting machine, a support, a

tank containing combustion supporting gas detachably connected with said support, a pressure reducing valve detachably secured to and supported from said tank and having communication therewith, said pressure reducing valve having two outlet passages, a mixing chamber supported from said pressure reducing valve and having communication with one of said outlet passages, said mixing chamber also having communication with a source of combustive gas, a discharge for 

